Eastern Tent Caterpillars in Fruit Trees

Eastern tent caterpillars hatch in early spring.

This spring, something pitched a tent in my crabapple tree. It’s a small, webby tent full of tiny wiggly things called – you guessed it – tent caterpillars, specifically eastern tent caterpillars. Eastern tent caterpillars live in, well, the east, and they’re the larvae of something imaginatively named – get ready for it – the eastern tent caterpillar moth. They prefer fruit trees such as cherry, apple, and crabapple, although they’ll show up in other trees as well.

Eastern tent caterpillars are one of the earliest critters to start wiggling in spring, and they can be anything from a novelty to a downright nuisance. Here’s what you need to know if eastern tent caterpillars pay you a visit this year.

A close-up of the growing critters inside their tent.

The Story of the Tent Caterpillar

Sometime last fall, as the grand finale of her life cycle, a female moth tucked a mass of eggs into a branch of my crabapple tree. The eggs were camouflaged with a brown coating that protected them through the winter. Early this spring, just as the leaves started budding on the trees, the eggs hatched into tiny caterpillars, which quickly set to work pitching their tent around a branch.

This tent is their home base while they go about munching the leaves of the tree. They’ll hang out here for about six weeks, growing to about two inches long, before setting out in all directions, looking for the best place to spin their cocoons and work on turning into moths. Look for the brown adult moths fluttering around your porch lights in early summer.

Eastern tent caterpillars are harmless to humans and usually nothing to worry about. If a tree becomes badly infested, the entire tree may become covered in silk tents, and the caterpillars can eat it bare. Trees usually recover from the occasional infestation, but if it goes on year after year you’ll see a decline in the health of the tree. I’m keeping an eye on my crabapple, but I’m not worried about this one little tent; in fact, I’m eager to follow their progress.

So far, they’re only snacking on the leaves close to their tent.

How To Control Eastern Tent Caterpillars

If a severe infestation of eastern tent caterpillars is damaging your trees or really insulting the aesthetic of your yard, here are a couple of options:

• Destroy Eggs: Learn to identify the egg masses in the fall and destroy them before they hatch.
• Remove Caterpillars: Use a stick to pull down the tent web and spread the caterpillars around to be gobbled up by hungry birds, or destroy them yourself. Choose a cool or rainy day when the caterpillars are likely to be hunkered down in the tent.
• Organic control: Pesticides don’t work very well on tent caterpillars, and they’re really not worth attacking unless they’re killing your trees. If necessary, they can be controlled organically with Bacillus thuringiensis kurstaki (Btk), a natural bacteria that kills caterpillars. Keep in mind that Btk also kills butterfly caterpillars, so use it very carefully and only where tent caterpillars are feeding.

Further Information

• Eastern Tent Caterpillar (University of Kentucky) Great information as well as photos of egg clusters and adult moths.
• Moth Caterpillars (Duke University) Photos of lots of different moth caterpillars.